Chlorosilanes



Patented Oct. 27, 1953 CHLOROSILANES George H. Wagner, Kenmore, N. Y., assignor to Union Carbide and Carbon Corporation, a corporation of New York No Drawing. Application June 21, 1949, Serial N 0. 100,529

14 Claims.

It is well known that chlorine-containing silicon compounds can be formed by subjecting silicon at an elevated temperature to the action of chlorine or chlorine compounds, for example, alkyl chlorides or hydrogen chloride. A number of metals are known to catalyze such reactions to some extent, for example, nickel, tin, silver, copper, antimony, manganese and titanium. Compositions containing silicon and a catalytic metal have been prepared in many ways and proportions, as by alloying or by mixing the powdered materials. Copper and other catalytic metals have been deposited on silicon by the reaction where M is the catalytic metal. The resulting compositions have been subjected to various conditioning treatments, such as grinding, sintering, etc.

No catalyst-containing mix has been found which is entirely satisfactory for all such reactions involving silicon and chlorine. On the contrary, the compositions, frequently called masses, are more or less specific in action, one which is preferable under one set of conditions being inferior under other conditions. Moreover, the behavior of the silicon-catalyst combination does not depend merely on chemical constitution as shown by analysis but on factors such as physical condition, traces of adsorbed gases and the like, most of which are not well understood.

The present invention relates to a catalytic mass for use in the preparation of chlorosilanes and to the preparation of chlorosilanes by the action of hydrogen chloride or alkyl chlorides on silicon. One object of the invention is to improve the elilciency of such processes. A more specific object is to provide a process of this kind giving a substantial yield of dichlorosilanes which are particularly useful in synthesizing organo-silicon compounds.

Copper has long been recognized as a catalyst for preparing SlHCls and sick. However, it appears from the reports in the literature that such copper-catalyzed masses as have been used in this connection give low yields of dichlorosilane, or no detectable quantity.

, I have discovered that a superior mass for the preparation of the chlorosilanes can be made by plating copper onto particles of silicon from a hydrogen fluoride bath of a copper salt. A greatly improved reaction mixture can be obtained by holding the mass of copper plated silicon for a time at an elevated temperature. The following example is illustrative:

Silicon was ground to between and mesh fineness. A slurry of the ground silicon in Water was prepared. A water solution of copper sulfate and hydrogen fluoride in a molecular ratio of about one part copper sulfate to two parts hydrogen fluoride was added to the slurry. The silicon particles were coated uniformly with copper which comprised approximately 6% by weight of the copper-silicon mass. The mass of copper coated silicon was then heated for about fifteen hours at a temperature of from 950 to 1000 C. The heat treated mass was cooled and a mixture of hydrogen and hydrogen chloride in a molecular ratio of about 4:1 was passed over the mass at the rate of 2.5 cubic feet per hour while the temperature was held at 350 C. The volatile silicon containing products were condensed and separated by fractional distillation. Dichlorosilane, SiHzClz, constituted slightly more than 30% of the condensate.

Other methods of combining silicon and copper salts in the presence of hydrogen fluoride can be adopted without departing from the scope of this invention. For example silicon can be added directly to a water solution of a copper salt and hydrogen fluoride. The slurry of silicon in water as used in the test described is merely illustrative of the manner in which the plating of copper on silicon in the presence of hydrogen fluoride can be accomplished.

The proportion of copper in masses prepared in accordance with my invention is not critical. Best results are obtained if the Weight of copper is not less than 1% nor more than 25% of the Weight of the mass.

It will be understood that copper can be plated onto silicon from hydrogen fluoride baths of all Water soluble copper salts and this invention is not limited to the use of copper sulfate. Among the salts that have been found satisfactory are copper nitrate, copper acetate, cupric chloride and cuprous chloride. The ratio of hydrogen fluoride to the copper salt does not appear to be critical; however, to obtain an even coating of copper in a reasonable time, a molecular ratio of at least two parts hydrogen fluoride to one part copper salt is preferred.

The plated mass can be heated at different tem peratures and for various periods of time, but a treatment for a minimum of three hours at a temperature of at least 900 C. is considered desirable. In general as the temperature is decreased the time of treatment must be increased. The preferred heat treatment is that described 3 in the example above of hours at a temperature of 950 to 1,000 C.

The reaction between the copper-silicon mass and hydrogen chloride produces good yields of dichlorosilanes as Well as other chlorosilanes at temperatures ranging from 250 to 450 C. The amount of dichlorosilane-v in the'product averages about 28% at "temperatures of 335 to:430-C; and: decreases somewhat at lower or higher temperatures.

The presence of hydrogen in the stream oihydrogen chloride which passes over the coppersilicon mass serves to dilute the reactantszand. aids in controlling the reaction. Argon' orother non-oxidizing gases can be substituted for the hydrogen or the diluents can be. omitted. with-- out departing from the scope of the inventiornv Satisfactory yields of ohlorosilanes have been obtained with hydrogen-to-hydrogen chloridera ties up to to 1.

The mass -:of the invention can'alsozbezemployed in. the manufacture of they methylzchlorosila-nes and; homolcgues. thereof: In one. test methyl. chlorideCEsCl was :passedover. abed-of. the-zcope per-silicon mass; at 400 C. The; mass-contained: about 10%plated copperrby. weight ;and-.1had.;been; heat treated ion lfixhours at 950-100.'0"C... The. volatile productwhich was. condensed: and .sepasratediby fractional'distillation, contained: 1556 CHs'S'iCls,19.1%.CH3S1HC12; 51.1% (CI-I392 SiC12-,. 7.3 (CH3): SiCLremaindedSiI-ICls: and $1014..

Thelcop-per-silicon mass preparedaccording to this invention: has provediitself to. be generally efficaciouszin the production of .chlorosilanes and: particularly. in .the production; of. dichlorosilanesl Asshoivnaheve; the combinationvof the massnf; the. invention with either. hydrogen chloride or: alkyl chlorides results inihigh.yields=ofizdichloro-- silanes. In theappended claimszthe term. RC1. will be used to designate the classof'materials comprisinghydrogen chloridezandrthe -.alkyl chlorides:

While the: foregoing description refers to 'the use of"silicon inxmaking-the catalyzed masses it will be understoodlthat this-term embraces-all silicon-containing compositions andia'lloys' whichv aresufiiciently free from:interferingeimpunities.

This: application isain'. part a. continuation of my; co .-pendingo application, .U. S.-.l? atentr 2;499;00'9: issued February 28, 1950.

I claim:

1. vAxprocess:forxthe production of ch'lorosilanes comprisingrthe steps of mixing:- particles 0f silicon with awater solution of hydrogenfiuoride and a copper salt to form a mass of copper-coated silicon particles;- reacting said masswitlr hydrogen chloride, and-recovering a chlorosilanee 2. A processior the production of chlorosil'a'nes comprising the steps of mixing particles of siliconwith a:watersolutionofihydrogen fluoride-and a' copper salt to form:a;mass of coppencoated silicon? particles, heating said. mass. ion at. least; three: hours at a temperaturerof 'at' least 900 C.,.r.eact:- ing said mass with hydrogen chloride;. and: re:.-- covering a chlorosilane;

3. A process for the;productionoi'chlorosilanes: comprising the steps of mixing particlesiof. silicon with a water solution of hydrogen fluoride-and a copper salt to form a mass of. copper coatedsilicon particles, heating; said mass for: atleastthree; hours at a-temperaturejof;atleast900 reacting; said mass with hydrogen chloride; at aitemperae ture of 250 to'450'C. and.recoveringa-aichloros silane.

4. A process for the production of chlorosilanes comprising the steps of mixing particles of silicon with a water solution of hydrogen fluoride and a copper salt to form a mass of copper coated silicon particles, heating said mass for at least three hours at a temperature of at least 900 C'., reacting said mass with hydrogen chloride in the presence ofanon-oxidizing gas at a temperature of 250 to 450 C. and recovering a chlorosilane.

5. A process for the production of chlorosilanes comprising the steps of mixing particles of silicon with a Water solution of hydrogen fluoride and a coppersaltrto.rormiaanass of copper coated silicon particles; reacting said mass with an alkyl chloride ancl recoveri-ngan alkyl chlorosilane.

6; Aprocession the production of chlorosilanes comprising the steps of mixing particles of silicon with a water solution of hydrogen fluoride and a copper salt to form a mass of copper coated silicon particles, heating said mass for at least three hoursiat'za .teinperaturewofiati least:;900 (3.; reactingsaid :mass with: an .alkyl chloride, and;r.ecover-- ing an alkyl chlorosilane;

'7. A process for the aprcduction of: chlorosilanes comprising the steps ot: mixing particles ofrsilicon. with a water solution oizhydrogenfiuoride and a copper :salt :to form aimassiof copper coated silicon particles heating said; mass; for at least. three. hours at-ta temperature :of ..at least .900? C., react ingsaidimass with.an1aikylzchloride ataitemperatureaof. 250.'to.450.i"C. and recovering: an alkyl chloro'silane';

8-.2 Ailprocessnfor. the.productionaofcli'lorosilanes. comprising the steps oflmix-ing particles of silicon with a Water solution of hydrogen fluoride and a copper saltflto :forrn- -a m'assof copper coated silicon particles,- heating said mass for at: least three hours' at a temperatureofatheist-900 Ci, reacting said mass with an aliryl chloride in the pres-- ence of a-n'on-oxidizinggasat'a' temperature of 25'0?- to 450 C. andrecovering an alkyl chloro-- sil'ane;

9. A; process for the-productionof chlorosilan'escomprising the steps of mixing particles of silicon with a: water solution of hydrogenfluoride and" a" copper salt to :formamass-of copper-'co'atedsilieon particles, reacting said H1255" with: RCl; R representing at least one of the materials inthe'g-roup' consisting ofhyd'rogen andthe alkyl radicals" and recovering:achlorosilanez 10. A process for the production of chlorosilanes comprising 1 the steps of mixingparticles o fisiliconawith awater solutionof hydrogen fluoride and a copper salt to form a mass of coppercoatedsiliconwparticles he'ating'said mass for at least; three hours at 'a t'emperatureoi at least 900 C., reacting said niass with RC1, R representing at :least one of the materials in thegroup consist-- ing. of. hydrogen and the alk-ylradicals; and recovering. a ohlorosil'ane.

11. A process for the production of chloros lanes comprising the steps'oi mixing-particles of SlllCOIl' with a water solution of hydrogen'fi'uoride and a copper salt to iorm a mass of copper-coated silicon. particles, heating said'rnass for" at least three hours at a temperature of'at" least 900 C. reacting said mass with RC1} R representing at least'onev of the-materials-in thegroup consistmg of; hydrogen and thealkyl'radicals; at atem perature of. 250 to 450 C. and recovering a chlorosilane.

l2.'.A process for the production of. 3 10 s lanes comprising theystepszof mixing particles-of 51110011 with a water solution of hydrogenfiuorideand a copper salt to form a massofcopper-coatedl silicon particles, heating said mass for at least three hours at a temperature of at least 900 0., reacting said mass with R01, R representing at least one of the materials in the group consisting of hydrogen and the alkyl radicals, in the presence of a non-oxidizing gas at a temperature of 250 to 450 C. and recovering a chlorosilane.

13. A copper-silicon chemical reactant mass formed by mixing particles of silicon with an aqueous solution of hydrogen fluoride and. a copper salt whereby a substantially uniform coating of copper is deposited on said silicon particles.

14. A copper-silicon chemical reactant mass formed by mixing particles of silicon with an aqueous solution of hydrogen fluoride and a copper salt, depositing on said particles of silicon from said solution a substantially uniform coating of copper equal to from 1% to 25% of the 6. weight of said mass and then heating said mass for at least three hours at a temperature of at least 900 C.

GEORGE H. WAGNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,420,912 Hurd May 20, 1947 2,447,873 Rochow Aug. 24, 1948 2,464,033 Gilliam Mar. 8, 1949 2,466,413 Gilliam Apr. 5, 1949 2,532,430 Strother et al Dec. 5, 1950 OTHER REFERENCES Hurd, Jour. Am. Chem. $00., vol. 67, July 1945, pages 1057-1059. 

5. A PROCESS FOR THE PRODUCTION OF CHLOROSILANES COMPRISING THE STEPS OF MIXING PARTICLES OF SILICON WITH A WATER SOLUTION OF HYDROGEN FLUORIDE AND A COPPER SALT TO FORM A MASS OF COPPER COATED SILICON PARTICLES, REATING SAID MASS WITH AN ALKYL CHLORIDE AND RECOVERING AN ALKYL CHLOROSILANE. 